linking heroin to creativity wasn't exactly a huge stretch; there have been many talented people who have been opiate/general drug addicts.
That's the cliché and the myth. The creativity was always there in those people. Heroin is what stifles it, what makes you loose your passion, and consumes all your time.
It doesn't make you write better songs, or paint better, or write better. All it does is make you a dope fiend. Read any interviews with recovering addicts like Slash, Scott Weiland, etc, and they'll tell you the same thing. I'm sure Cobain and Staley would say the same thing if they were alive.
A lot of people start using dope, because they have this glamours image in their mind that it'll make them "deeper" and more "creative". It's a big reason why I started. I was young and all my idols did it.. I was a budding musician and artist at the time.
Truth, is every opportunity I got in the music or art world, heroin ruined. Too strung out to practice, make it through recording sessions, write new material, make it through a gig etc. I know a lot of musicians and artists who were strung out and it wasn't until they were clean, that they actually got serious and successful with their passion.
Heroin is not a tool for creativity. It is its destruction. The idea that it's going to help you with anything artistic is a young and naive notion, that is later blatantly disproven after you've actually become a heroin addict.